A laser-welded joint structure between insulation frame and bearing cup of fan includes a base having a bearing cup and a stator having at least one insulation frame. The insulation frame includes a sleeve portion defining a bore axially extending therethrough. The sleeve portion is provided on an inner wall surface with at least one pressing section that radially projects into the bore to press a lower side against an upper end of the bearing cup and a bearing received therein. A portion of at least one lateral side of each pressing section that is in contact with the upper end of the bearing cup is melted by laser beam to form a laser-welded joint, so that the insulation frame and the bearing cup are integrally connected together at reduced manufacturing cost and have increased structural strength. A method of forming the laser-welded joint structure is also disclosed.